Impact-resistant polyoxymethylene molding compositions, use thereof and moldings produced therefrom

Abstract

The present invention relates to a polyoxymethylene molding composition comprising: (A) from 0.1 to 5.0% by weight of a compatibilizer, (B) from 5 to 50% by weight of an impact modifier, (C) the remainder to 100% by weight of a polyoxymethylene. The molding compositions of the invention have substantially improved mechanical properties, in particular impact resistance.

1. A polyoxymethylene molding composition comprising
 (A) from 0.1 to 5.0% by weight of a compatibilizer containing underlying units of the following formula: 
 
       
         
           
           
               
               
           
         
       
       where R and R 2  are a hydrogen atom or an alkyl group having 1 or 2 carbon atoms, 
       
         
           
           
               
               
           
         
       
       and where X is CH 3  or 
       
         
           
           
               
               
           
         
       
       and at least one X is 
       
         
           
           
               
               
           
         
       
       and where 
       a is a number from 1 to 10, 
       b is 0 or 1, 
       c is a number from 0 to 10, 
       l is a number from 0 to 10, 
       R 3  and R 5  are hydrogen atom or a methyl group, 
       R 4  is a hydrogen atom or an alkyl group having from 1 to 4 carbon atoms, 
       m is 1 or 2, 
       n is 0 or 1 or 2, 
       x is an integer from 0 to 10, 
       Y is H or 
       
         
           
           
               
               
           
         
       
       where 
       R 6  and R 7  are identical or different and are an alkyl group having from 1 to 4 carbon atoms, 
       R 8  is an alkyl group having from 1 to 12 carbon atoms, phenyl, alkylphenyl or cycloalkyl having from 3 to 12 carbon atoms 
       
         
           
           
               
               
           
         
       
       where the underlying units of the formula (Ia), (IIa), (IIIa), (IVa) and (Va) may have bonding to underlying units of the formula (I), (II), (III), (IV), or (V), and the compatibilizer comprises
 from 29 to 70% by weight of underlying unit of the formula (I) 
 from 0.5 to 30% by weight of underlying unit of the formula (II) 
 from 10 to 70% by weight of underlying unit of formula (III) 
 and from up to 10% by weight of underlying units of the formula (IV) and/or (V), 
 (B) from 5 to 50% by weight of an impact modifier, 
 (C) from 0 to 40% of conventional additives selected from the group consisting of carbon blacks, acid scavengers, antioxidants, stabilizers, UV stabilizers, coupling agents, mold-release aids, substances to improve electrical conductivity, antistats, nucleating agents, colorants, fillers, lubricants, waxes, oils, and combinations thereof, 
 (D) the remainder to 100% by weight of a polyoxymethylene. 
 
     
     
       2. The polyoxymethylene molding composition as claimed in  claim 1 , wherein component (B) comprises a polyurethane, a two-phase mixture made from polybutadiene and styrene-acrylonitrile (ABS), modified polysiloxanes, silicone rubbers, of graft copolymers in a core-shell structure comprising an elastomeric, single-phase core based on polydiene, or mixtures thereof. 
     
     
       3. The polyoxymethylene molding composition as claimed in  claim 1 , wherein component (B) comprises graft polymers made from an elastomeric, single-phase core based on polydiene and an outer graft layer forming a core-shell structure, the outer layer of the particles having one or two subshells, where, in the case of particles having one subshell, the shell is composed of poly(meth)acrylate and poly(meth)acrylonitrile, and, in the case of particles having two such shells, the inner subshell is composed of crosslinked polystyrene and the outer subshell is composed of crosslinked polymethacrylate. 
     
     
       4. The polyoxymethylene molding composition as claimed in  claim 1 , wherein component (D), the polyoxymethylene, has been prepared using trifluoromethanesulfonic acid or boron trifluoride as initiator. 
     
     
       5. A molding produced from a thermoplastic molding composition as claimed in  claim 1 . 
     
     
       6. The polyoxymethylene molding composition as claimed in  claim 1 , wherein said compatibilizer comprises underlying units of the formula (I), (II), (III), and (IV). 
     
     
       7. The polyoxymethylene molding composition as claimed in  claim 1 , wherein said compatibilizer comprises underlying units of the formula (I), (II), (III), and (V). 
     
     
       8. The polyoxymethylene molding composition as claimed in  claim 1 , wherein said compatibilizer comprises underlying units of the formula (I), (II), (III), (IV) and (V). 
     
     
       9. The polyoxymethylene molding composition as claimed in  claim 1 , which comprises
 (A) from 0.2 to 2% by weight of a compatibilizer, 
 (B) from 5 to 40% by weight of an impact modifier, 
 (C) the remainder to 100% by weight of a polyoxymethylene. 
 
     
     
       10. The polyoxymethylene molding composition as claimed in  claim 1 , which comprises
 (A) from 0.3 to 0.6% by weight of a compatibilizer, 
 (B) from 7 to 30% by weight of an impact modifier, 
 (C) the remainder to 100% by weight of a polyoxymethylene. 
 
     
     
       11. The polyoxymethylene molding composition as claimed in  claim 6 , which comprises
 (A) from 0.3 to 0.6% by weight of a compatibilizer, 
 (B) from 7 to 30% by weight of an impact modifier, 
 (C) the remainder to 100% by weight of a polyoxymethylene. 
 
     
     
       12. The polyoxymethylene molding composition as claimed in  claim 7 , which comprises
 (A) from 0.3 to 0.6% by weight of a compatibilizer, 
 (B) from 7 to 30% by weight of an impact modifier, 
 (C) the remainder to 100% by weight of a polyoxymethylene. 
 
     
     
       13. The polyoxymethylene molding composition as claimed in  claim 8 , which comprises
 (A) from 0.3 to 0.6% by weight of a compatibilizer, 
 (B) from 7 to 30% by weight of an impact modifier, 
 (C) the remainder to 100% by weight of a polyoxymethylene. 
 
     
     
       14. The polyoxymethylene molding composition as claimed in  claim 1 , which comprises from 0.2 to 2% by weight of the compatibilizer. 
     
     
       15. The polyoxymethylene molding composition as claimed in  claim 1 , which comprises from 0.3 to 0.6% by weight of the compatibilizer. 
     
     
       16. The polyoxymethylene molding composition as claimed in  claim 1 , which comprises from 5 to 40% by weight of the impact modifier. 
     
     
       17. The polyoxymethylene molding composition as claimed in  claim 1 , which comprises from 7 to 30% by weight of the impact modifier.